Don't try to start the compressor immediately after it has been running (short-cycling) it will be nearly impossible even with the 3'n1. Give it at least 20 minutes between shutdown and restart. Test the whole thing under real-world conditions before you condemn it. Give us a running amp draw after the compressor has been running at least 2 minutes. Did you mention how old this unit is? Might have a 5-year warranty on the compressor.

____________________"When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth." Sir Arthur Conan Doyle.